MonadError example

MonadErrorExample.scala

import cats.MonadError
import cats.instances.either._
import cats.instances.future._
import cats.instances.try_._
import cats.syntax.applicativeError._
import cats.syntax.flatMap._

import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration._
import scala.concurrent.{Await, Future}
import scala.util.Try

object MonadErrorExample {
  type ThrowableEither[A] = Either[Throwable, A]
  type ThrowableMonadError[F[_]] = MonadError[F, Throwable]

  def safe[F[_] : ThrowableMonadError](): F[Int] = {
    val errorHandler = implicitly[ThrowableMonadError[F]]

    errorHandler.catchNonFatal {
      5 / 0
    }.recoverWith {
      case ex => errorHandler.catchNonFatal {
        15 / 0
      }
    }.flatMap { result: Int =>
      errorHandler.pure(10)
    }.recover {
      case ex => 1
    }
  }

  safe[Try]()
  Await.result(safe[Future](), 10 seconds)
  safe[ThrowableEither]()
}